QUASI-COLLISIONLESS MAGNETIC RECONNECTION EVENTS IN THE NEAR-EARTH MAGNETOTAIL

Hot ion (- 5 eV/e-32 keV/e) and magnetic field data observed by Cluster Ⅱ-C1 CIS/HIS and FGM during the magnetotail plasma sheet crossing on September 15, 2001 are analyzed in this paper. In the interval of 0340-0440 UT, fast tailward ion flows (V_XGSM < 0) were observed, which were associated with the enhancements of southward and dusk-downward magnetic fields (B_ZGSM < 0 and B_YGSM < 0 or > 0). It can be inferred from these observations that magnetic reconnection events took place at X_GSE > -18.6 R_e within the plasma sheet in the interval of 0340-0440 UT on September 15, 2001. The characteristics for these events are consistent with the physical pictures of theory for a quasi-collisionless magnetic reconnection. Hence these events should be called as quasi-collisionless magnetic reconnection events.